Charging rate reduces on my T61's battery

[darthshak]

I purchased a Thinkpad T61 in October 2007. There are some very interesting issues I ran into while using it.
I used Ubuntu for over a year and a half, and for the last few weeks have been using OpenSUSE. The design capacity of my battery was 65.52 Wh. To my shock, I found that it had dropped to 56 Wh. I know this was to expected of Li-ion batteries, but I knew that it is likely that the gauge was giving an incorrect reading.

Nonetheless, I knew for a fact that Gauge resets are not a good idea on Li-ion batteries, and the Lenovo site indicates the same fact. I decided to manually run down the battery couple of times in a week, and found that the capacity had "gone up" to 61.15 Wh.
Indeed, I was able to get a lot more run time (up to an additional hour of run time) on battery.

However, after another week or so, I found that the capacity had again gone down to 58 Wh. I tried doing a battery rundown with IBM PC doctor, and well, there was no improvement at all.

Does anyone know how exactly the reading came up to 61.15 Wh at one point, and then dropped to 58?
Also, the charging rate of the battery when I plug in the laptop starts at around 20 W and reaches 4 W or so just when the battery is about to reach the fully charged state.

[killer]

Anyhow, as JaneL points out quite correctly, Thinkpad batteries are like car batteries or torch batteries in that you are never quite sure how long they will last or when they will work.

Meanwhile you could suffer a heart attack from over-monitoring your battery. Buy a new one and breathe safely again.

[dr_st]

Does anyone know how exactly the reading came up to 61.15 Wh at one point, and then dropped to 58?

That's normal. When you reset the gauge, it often overshoots or undershoots as to what the true capacity is. So in reality, your capacity is somewhere between 56 and 61. 58 seems plausible. Losing only 7Wh after a year and half, you cannot complain.

Also, the charging rate of the battery when I plug in the laptop starts at around 20 W and reaches 4 W or so just when the battery is about to reach the fully charged state.

That's also normal. That's how electricity works. When the capacitor is empty, it charges fast, and the charge rate becomes exponentially slower as it reaches full capacity.